# Thread: Word problem with differential equations?

1. ## Word problem with differential equations?

Am having trouble with finding the equations for word problems of differential equations. Did I get these two right? If not, which one is right for the problem?

2. ## Re: Word problem with differential equations?

If that is all you want to know, then the first is wrong, the second is right.

If you want to know why the first is wrong and the second right, you will need to tell us why you thought they were correct.

3. ## Re: Word problem with differential equations?

Originally Posted by HallsofIvy
If that is all you want to know, then the first is wrong, the second is right.

If you want to know why the first is wrong and the second right, you will need to tell us why you thought they were correct.
Okay, I just redid the first one and got the same answer :/. I used the compounding formula: A=p(1+r)^n For this it would be: B=50(1 + 0.05/12)^12t And subtracting the money put in by the mom. Wouldn't that give me A?

4. ## Re: Word problem with differential equations?

I must be missing something - the first term is the interest - 0.05B/12 (monthly interest times principal). Mom puts in 240/6 = 40 a month, and Saleem takes out 50 a month, so that gives -10 for the other term. So isn't A correct?

- Hollywood

5. ## Re: Word problem with differential equations?

Originally Posted by hollywood
I must be missing something - the first term is the interest - 0.05B/12 (monthly interest times principal). Mom puts in 240/6 = 40 a month, and Saleem takes out 50 a month, so that gives -10 for the other term. So isn't A correct?

- Hollywood
I thought so! I wasn't extremely sure but after writing it all out that's what I had. Thanks